1. Field of the Invention
The present invention relates to a magneto-resistive effect type magnetic head that reproduces the data recorded on a magnetic tape, and to a magnetic tape apparatus that has a magneto-resistive effect type magnetic head.
2. Related Art
Hard disc drives are known as magnetic disc apparatus that record and reproduce data on and from magnetic discs. Generally, a hard disc drive has a magneto-resistive effect type magnetic head (hereinafter referred to as xe2x80x9cMR headxe2x80x9d). The MR head has a width smaller than the width of the recording tracks of a magnetic disc. Note that the width of the MR head is measured in the widthwise direction of the recording tracks.
As shown in FIG. 1, the magnetic disc incorporated in a hard disc drive has concentric recording tracks T2. A guard band 50 is provided between any two adjacent recording tracks T2. As FIG. 1 shows, the MR head 51 provided in the hard disc drive is if SAL (Soft Adjacent Layer) type. The MR head 51 is subjected to on-track control and is thereby positioned within the width W0 of a recording track T2. The data-reproducing ability of the MR head 51 is evaluated by measuring the efficiency at which the MR head 51 reproduce data from the entire width W0 of the recording track T2.
It is proposed that an MR head of the type described above be applied to a magnetic tape apparatus such as a video tape recorder. The magnetic head incorporated in a magnetic tape apparatus is designed to record and record data on and from a magnetic tape, along a line inclined at a prescribed azimuth angle to the widthwise direction of the recording track of the magnetic tape. That is, the magnetic tape apparatus has a rotary head mechanism of so-called. xe2x80x9chelical scan system,xe2x80x9d in order to record data on, and reproduce the same from the magnetic tape.
The rotary head mechanism used in the magnetic tape apparatus comprises an inductive magnetic head (hereinafter referred to as xe2x80x9cinductive headxe2x80x9d), an MR head, a rotary drum, a stationary drum, and a drive motor. The inductive head is provided to record data on a magnetic tape. The MR head is used to reproduce data from the magnetic tape. The rotary drum holds the inductive head and the MR head. The stationary drum supports the rotary drum, by using an axle. The drive motor is provided to rotate the rotary drum on the axle.
The inductive head comprises a magnetic core and a coil wound around the magnetic core. The magnetic core is composed of a pair of core halves, which constitute a closed magnetic path. The magnetic core has a magnetic gap that is very narrow. The MR head has a magneto-resistive effect element (hereinafter referred to as xe2x80x9cMR elementxe2x80x9d). The rotary drum is a bottomed hollow cylinder made of metal. The axle supports the rotary drum, at the center of the bottom thereof. The inductive head and the MR head are secured to the outer circumferential surface of the rotary drum. The stationary drum is a bottomed hollow cylinder made of metal and supports the axle, allowing the same to rotate. Hence, the stationary drum holds the rotary drum by the use of the axle.
In the magnetic tape apparatus thus constructed, the magnetic tape runs, sliding on the outer circumferential surface of the rotary drum. The inductive head records data on the recording track of the running tape, along a line inclined at a prescribed azimuth angle to the widthwise direction of the recording track. As the magnetic tape runs, the MR head reads data from the recording track of the magnetic tape.
The efficiency at which the inductive head records data on the entire width of the recording track is measured, for example, right after the above-described magnetic tape apparatus is manufactured, thereby to evaluate the data-recording ability of the inductive head and the data-reproducing ability of the MR head.
As long as no external magnetic field is applied to the MR head from the magnetic tape, the MR head is magnetized usually at 45 degrees to the direction in which a sense current flows in the MR head. When an external magnetic field is applied to the MR head while a current is flowing from one end of the MR head to the other end thereof, the ends of the MR head are magnetized at different angles. That is, the MR head can no longer have uniform data-reproducing characteristic, depending upon the direction of easy magnetization. The data-reproducing characteristic of the MR may fail to be uniform, too, unless the MR head is magnetized uniformly.
The MR head is inevitably more likely to exhibit non-uniform data-reproducing characteristic than the inductive head, depending on the position it takes in its widthwise direction that is parallel to the widthwise direction of the recording track. This fact must be taken into full consideration in evaluating the data-reproducing ability of the MR head.
The inductive head, which is incorporated in the rotary head mechanism, records data on a recording track, while writing the data over one side of the immediately adjacent track on which data has just been recorded. Thus, the azimuth angle for the recording track differs from the azimuth angle for the immediately adjacent recording track.
However, the inductive head may not be secured to the rotary drum with a sufficient positioning precision. If so, the inductive head is inevitably displaced with respect to the widthwise direction of a recording track. Consequently, adjacent recorded tracks will have different track widths W1, W2 and W3, as is shown in FIG. 2. In other words, the magnetic tape will have recorded tracks that differ in terms of their widths.
As shown in FIG. 2, the MR head 55 may not be secured to the rotary drum with a sufficient positioning precision. In this case, the MR head 55 is displaced in its widthwise direction W2 with respect to the width W1 of the recorded track T3. That is, the MR head 55 takes various positions A, B, C, D and E shown in FIG. 2, inevitably located off the track. If located so, the signals the MR head 55 reproduces at the positions A, B, C, D and E will differ from one another, when its data-reproducing characteristic is not uniform over the entire head width W2. In other words, the MR head 55 exhibits a defect that the data reproducing characteristics vary depending on each position A, B, C, D and E.
In view of the above-described problems, it is necessary to evaluate the data-reproducing characteristics (hereinafter referred to as xe2x80x9cmicro-track characteristicxe2x80x9d) the MR head 55 exhibits at the off-track positions A, B, C, D and E which are off-tracked in the direction of the track width W2 of the recording track T3. Note that the MR head 55 reproduces data from the track T3 on which data has been azimuth-recorded by helical-scan method.
The MR head, which is incorporated in the rotary head mechanism, is displaced in the widthwise direction of a recording track when the recorded tracks vary in width. Whenever the MR head is displaced in the widthwise direction of the track, its data-reproducing characteristic changes very much.
Accordingly, an object of this invention is to provide a magneto-resistive effect type magnetic head that can reliably reproduce data from a magnetic tape.
Another object of the present invention is to provide a magnetic tape apparatus that can reliably reproduce data from a magnetic tape.
To attain the first-mentioned object, a magneto-resistive effect type magnetic head according to the invention comprises a magneto-resistive effect element for reproducing data recorded on a magnetic tape at a prescribed azimuth angle to the direction of width of a recording track of the magnetic tape. The magneto-resistive effect type magnetic head has a head width greater than the width of the recording track, as measured in the width direction of the recording track. The magneto-resistive effect element has a magnetism-detecting section arranged at the prescribed azimuth angle. The signal reproduced from the magnetic tape as the head is moved while off-tracked in the widthwise direction of the recording track has a specific characteristic value that falls within a predetermined range for a reference value within the predetermined range of the width direction of the bead.
The magneto-resistive effect type magnetic head reproduces data recorded on the magnetic tape at the prescribed azimuth angle to the direction of width of a recording track of the magnetic tape. The head is moved while off-tracked in the widthwise direction of the recording track, thereby reproducing a signal from the magnetic tape. The signal produced has a specific characteristic value that falls within a predetermined range for a reference value. Thus, the magneto-resistive effect type magnetic head can reproduce data at high reliability.
To attain the other object mentioned above, a magnetic tape apparatus according to the invention comprises a rotary drum in which a magneto-resistive effect type magnetic head that has a magneto-resistive effect element for reproducing data recorded on a magnetic tape at a prescribed azimuth angle to the direction of width of a recording track of the magnetic tape is provided rotatively. The magneto-resistive effect magnetic head has a head width greater than the width of the recording track, as measured in the width direction of the tape. The magneto-resistive effect element has a magnetism-detecting""section arranged at the prescribed azimuth angle. The signal reproduced from the magnetic tape as the head is moved while off-tracked in the widthwise direction of the recording track has a specific characteristic value that falls within a predetermined range for a reference value within the predetermined range of the width direction of the head.
In the magnetic tape apparatus, magneto-resistive effect type magnetic head reproduces data recorded on the magnetic tape at the prescribed azimuth angle to the direction of width of a recording track of the magnetic tape. The head is moved while off-tracked in the widthwise direction of the recording track, thereby reproducing a signal from the magnetic tape. The signal produced has a specific characteristic value that falls within a predetermined range for a reference value. Thus, the magneto-resistive effect type magnetic head can reproduce data at high reliability.
The magneto-resistive effect type magnetic head according to the present invention can be quantitatively evaluated for its data-reproducing ability. The data-reproducing ability thus evaluated is high, and the magnetic head can therefore reproduce data at high reliability.
The magnetic tape apparatus according to the present invention has a magneto-resistive effect type magnetic head that can be quantitatively evaluated for its data-reproducing ability. Therefore, the apparatus can reproduce data from magnetic tapes, at high reliability.